The present application relates to a battery including a battery element in a battery can.
In recent years, a large number of portable electronic devices such as camcorders, cellular phones and laptop computers have been emerged, and an attempt to reduce the size and the weight of them has been made. Research and development aimed at improving the energy densities of batteries used as portable power sources of the electronic devices, specifically secondary batteries as key devices have been actively promoted. Among the batteries, non-aqueous electrolyte secondary batteries (for example, lithium-ion secondary batteries) can obtain a high energy density, compared to lead-acid batteries and nickel cadmium batteries which are aqueous electrolyte solution secondary batteries in related arts, so studies for improving the energy density have been conducted in various quarters.
Lithium-ion secondary batteries with various shapes have been developed, and among them, there is a lithium-ion secondary battery in which a cathode and an anode are laminated with a separator in between and are spirally wound to form a spirally wound body, and a cylindrical center pin made of metal or a resin material is inserted into the center of the spirally wound body (for example, refer to Japanese Unexamined Patent Application Publication Nos. H4-332481 and H11-204140).
FIG. 33 shows an example of a center pin in a related art. The center pin has a slit 131 in an axial direction of a cylindrical main body 130 made of, for example, metal. When an external force is applied to the battery, the main body 130 is crushed, and as a result, the edge of the slit 131 opens out, and the opened part penetrates the separator to establish a short circuit between the cathode and the anode. Thereby, a battery reaction is prevented to safely lose a power generation function.
However, in a secondary battery using a center pin with the above-described structure in the related art, the deformation of a slit portion in the case where the center pin is crushed by an external force is not sufficient, so it is difficult to reliably establish a short circuit between the cathode and the anode. Therefore, an effective technique for more reliably establishing a short circuit between electrodes to secure safety is desired.
Moreover, in a so-called prismatic battery using a rectangular battery can, a battery element formed by spirally winding a cathode and an anode to form a spirally wound body, and then forming the spirally wound body in a flat shape is used, so it is difficult to insert the above-described cylindrical center pin in the related art into the center of such a flat battery element.
Further, in the case of a large size battery, when the battery is crushed by an external force, it is difficult to obtain a sufficient effect of preventing power generation only by a short circuit by a center pin inserted into the center of a spirally wound battery element.
It is disclosed in Japanese Unexamined Patent Application Publication No. 2001-229905 that a perforated plate made of metal such as stainless steel is arranged between a closed end surface of a battery can and a bottom surface of a battery element, and gas-discharging holes are arranged in the center and a peripheral part of the perforated plate to guide a gas to a safety valve.